Differential fluid pressure motors



Jan. 24, 1956 w. E. O'SHEII DIFFERENTIAL FLUID PRESSURE MOTORS Filed Jan. 12, 1955 ATTORNEY United States Patent 2,731,954 DIFFERENTIAL FLUID PRESSURE MOTORS William Edward OShei, London, England Application January 12, 1953, Serial No. 3343,787

Claims priority, application Great Britain January 18, 1952 Claims. or. 121-186) The present invention relates to differential fluid pressure motors, such as suction motors as used for operating windscreen wipers, of the kind in which the automatic valve mechanism comprises a semi-rotary valve which is moved between its two positions for reversing the direction of movement of the motor piston or paddle by means of a kicker engaging spaced ears on the valve, the kicker being moved by the movement of the piston or paddle to a dead-centre position and is then actuated by an overcentre spring action to snap the valve quickly from one position to the other and vice versa.

The semi-rotary valve has hitherto been made from metal or other rigid material, and the movement of the kicker, after engaging an ear on the valve, stops moving before the valve has completed its full movement, the valve continuing to move by reason of its momentum for a short distance after the kicker stops and to become arrested against a valve stop. This arrangement is necessary since if the kicker were to remain in engagement with the ear of the valve when the latter comes to rest against its stop, there is a risk of the valve being tipped off its seating with resultant leakage occurring. This tipping of the valve and consequent leakage, may also occur upon the kicker engaging with an ear of the valve to move the valve to its other position, particularly when the motor is operating on low vacuum.

According to the present invention, the valve is moulded from a flexible synthetic rubber-like material integral with the ears against which the kicker is adapted to engage. According to a feature of the invention the complete automatic valve assembly being such that the kicker remains in contact with an car when the valve is in an extreme limiting position and is arrested by the valve stop. With this arrangement, not only is the valve positively moved to its extreme positions, thereby positively ensuring the ports being fully opened, but valve noise is also considerably reduced.

By reason of the flexible nature of the valve and its ears, even if the valve ears are tipped by the kicker being in engagement therewith when the valve is arrested by its stops, or when it engages an ear to tip the valve when the motor is operating on low vacuum, the cars can flex relative to the valve proper so that the valve is maintained in contact with the valve seating by the suction or fluid pressure applied thereto for operating the motor.

In order that the invention may be more clearly understood, an embodiment thereof will now be described with reference to the accompanying drawings, in which:

Fig. l is a front elevation of a suction operated windscreen wiper motor including a valve according to the invention and with the cover plate of the valve chamber removed, and

Fig. 2 is an exploded perspective view of the valve mechanism.

Referring to the drawings the motor comprises an arcuate chamber 1 in which oscillates a paddle 2 mounted on a rocker shaft 3. The paddle 2 has a portion beyond the rocker shaft 3 which oscillates within an auxiliary arcuate chamber formed on the top cover 6 of the motor chamber. The motor chamber 1 is formed with a valve chamber 7 on its outer face and the cover 6 is formed with complementary chamber 8, the chambers 7 and 8 together forming a chamber for the semi-rotary valve mechanism which controls the alternate application of suction to the motor chamber at opposite sides of the paddle. The valve chamber is normally provided with a cover which has been omitted in the drawings in order to show the valve mechanism.

The valve mechanism consists of a valve seating 9 formed in the rear wall of the chamber 8, this seating being formed with three ports 10, 11, 12, arranged symmetrically in angularly spaced relationship. The centre port 11 communicates through a channel 11a indicated in broken lines in Fig. 1 with a nipple 13 for connection to a source of suction, for example the intake manifold of an internal combustion engine. The port 10 communicates through a channel 14 shown in broken lines in Fig. l with the motor chamber on the left hand side of the paddle 2, as viewed in Fig. l, and the port 12 communicates through a similar channel 15 with the motor chamber on the right hand side of the paddle. As shown more clearly in Fig. 2, the valve mechanism comprises a semirotary valve member 16, freely mounted on the rocker shaft 3, and having a valve face 17 co-operating with the valve seating 9 and having an arcuate cavity 18 therein arranged to connect the port 11 to the port 10 in one of the two limiting positions of the valve member and to.

connect the port 11 to the port 12 in the other limiting position. According to the invention the valve member 16 is moulded from a flexible synthetic rubber-like material and is provided with a pair of cars 19 and 20 moulded integrally therewith. The ear 19 engages a stop 21 in one limiting position of the valve and the ear 20 engages a stop 22 in the other limiting position of the valve.

The valve member 16 is oscillated about the rocker" that the flat 28 engages one or other of the faces 26 or,

27 as the paddle approaches one or other of the two limiting positions so as to operate the kicker to reverse the suction connection. To this end the kicker is provided with a lug 29 movable between the ears 19 and 20 of the valve member so as to engage the ears alternately to oscillate the valve as the kicker is oscillated.

The kicker is operated with a snap action by means of an oven-centre spring 30 tensioned between one end of a pressure plate 32, carried on the rocker shaft 3, and the portion 33 of a stirrup member 34 which lies in front of the pressure plate 32 and engages in a slot in the kicker. The spring 30 serves the dual function of providing an over-centre spring for the kicker and of holding the pressure plate against the valve member 16 so as to press the latter against the valve seating 9 in the absence of suction. During operation of the motor, the suction within the cavity 18 which is permanently in connection with suction port 11 causes the valve member 16 to be held against the seating by atmospheric pressure.

The automatic valve mechanism is such that the kicker remains in contact with the ears 19 or 20 when the valve is in an extreme limiting position and is arrested by the valve stop. With this arrangement not only is the valve positively moved to its extreme positions against the stops 21 and 22, thereby positively ensuring the ports being fully opened, but valve noise is considerably reduced.

The flexible nature of the valve member 16 allows the Patented. Jan. 24, s

ears 19 and 20 of the valve to flex relative to the valve proper so that the latter is maintained in contact with the valve seating 9 by the suction within the cavity 13, even if the valve ears are tipped by the kicker. Similarly, if the valve ears are tipped upon the kicker engaging therewith to trip the valve, the latter is maintained in contact with the valve seating and leakage is prevented, even when the motor is operating on low vacuum.

Furthermore, a valve member moulded from a flexible synthetic rubber-like material according to the invention is more capable of absorbing the shock imparted to it, when its movement is suddenly arrested by the stop at the end of its travel, than the normally used rigid valve member. Thus fractures between the ears of the valve member and the valve body, caused by the hammering of the ears against the stops, and which may cause the ears to break off, are avoided.

The valve may be moulded from a synthetic rubber-like material. This material is oil resistant so that any oil on the surfaces between the valve and its seating will not perish the valve but will assist in allowing the valve to move freely over the valve seating. The movement of the valve will be further lubricated by reason of any moisture or dampness sucked into the motor which occurs particularly with windscreen wiper motors, which are operated under damp atmospheric conditions.

Whilst a particular embodiment has been described it will be understood that various modifications may be made without departing from the scope of the invention.

I claim:

1. An automatic valve for a differential fluid pressure motor, comprising a valve chamber having a valve seating, and an automatic valve mechanism within said valve chamber consisting of a semi-rotary valve having a valve face and a pair of spaced ears formed integrally therewith and made from a synthetic rubber having a degree of flexibility such that the cars can flex relative to said valve face, said valve being arranged so that said valve face can move over said valve seating between two limiting positions, a kicker adapted to engage said ears to move said semi-rotary valve between said two positions, and means for actuating said kicker including an over-centre spring mechanism to snap the valve quickly from one limiting position to the other.

2. An automatic valve for a differential fluid pressure motor, comprising a valve chamber having a valve seating, and an automatic valve mechanism within said valve chamber consisting of a semi-rotary valve having a valve face and a pair of spaced ears made from a synthetic rubber having a degree of flexibility such that the cars can flex relative to said valve face, said valve being arranged so that said valve face can move over said valve seating between two limiting positions, a kicker adapted to engage said ears to move said semi-rotary valve between said two positions and means for actuating said kicker including an over-centre spring mechanism to snap the valve quickly from one limiting position to the other.

3. An automatic valve for a differential fluid pressure motor, comprising a valve chamber having a valve seating, a stop member at each end of said valve seating, and an automatic valve mechanism within said valve chamber consisting of a semi-rotary valve having a valve face and a pair of spaced ears made from synthetic rubber having a degree of flexibility such that the cars can flex relative to said valve face, said valve being arranged so that said valve face can move over said valve seating between said two stop members, a kicker adapted to engage said ears to move said semi-rotary valve between said two stop members, means for actuating said kicker including a spring mechanism adapted to engage the kicker to snap the valve quickly from its position against one stop to its position against the other stop, and said kicker remaining in contact with an car when the ear is in contact with one of said stop members.

4. An automatic valve for a differential fluid pressure motor, comprising a valve chamber having a valve seating, a stop member at each end of said valve seating, and an automatic valve mechanism within said valve chamber consisting of a semi-rotary valve having a valve face and a pair of spaced ears formed integrally therewith and made from a synthetic rubber having degree of flexibility such that said cars can flex relative to said valve face, said valve being arranged so that said valve face can move over said valve seating between said two stop members, a kicker adapted to engage said ears to move said semirotary valve between said two stop members, means for actuating said kicker including a spring mechanism adapted to engage the kicker to snap the valve quickly from its position against one stop to its position against the other stop, and said kicker remaining in contact with an car when the ear is in contact with one of said stop members.

References (Iited in the file of this patent UNITED STATES PATENTS Hueber Aug. 27, Weidman Apr. 24, Rappl Aug. 7, Horton et al. Feb. 25, Buchmann Oct. 13, 1942 Fleming Oct. 26, 1943 OShei May 9, 1944 

